Re: up to a 20 per cent pay cut overnight... For many, the cost of their current mortgage
"and the rental income from my property after paying agency and other fees and 40% income tax on the rest does NOT cover the mortgage."
You've presumably told your bank, since that will probably result in the loan being called in, which will solve your problems :)
IIRC a standard BTL mortgage requires the rent to be 145% of the mortgage payment.